gprMax is open source software that simulates electromagnetic wave propagation, using the Finite-Difference Time-Domain (FDTD) method, for the numerical modelling of Ground Penetrating Radar (GPR). ...gprMax was originally developed in 1996 when numerical modelling using the FDTD method and, in general, the numerical modelling of GPR were in their infancy. Current computing resources offer the opportunity to build detailed and complex FDTD models of GPR to an extent that was not previously possible. To enable these types of simulations to be more easily realised, and also to facilitate the addition of more advanced features, gprMax has been redeveloped and significantly modernised. The original C-based code has been completely rewritten using a combination of Python and Cython programming languages. Standard and robust file formats have been chosen for geometry and field output files. New advanced modelling features have been added including: an unsplit implementation of higher order Perfectly Matched Layers (PMLs) using a recursive integration approach; diagonally anisotropic materials; dispersive media using multi-pole Debye, Drude or Lorenz expressions; soil modelling using a semi-empirical formulation for dielectric properties and fractals for geometric characteristics; rough surface generation; and the ability to embed complex transducers and targets.
Program title: gprMax
Catalogue identifier: AFBG_v1_0
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AFBG_v1_0.html
Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland
Licensing provisions: GNU GPL v3
No. of lines in distributed program, including test data, etc.: 627180
No. of bytes in distributed program, including test data, etc.: 26762280
Distribution format: tar.gz
Programming language: Python.
Computer: Any computer with a Python interpreter and a C compiler.
Operating system: Microsoft Windows, Mac OS X, and Linux.
RAM: Problem dependent
Classification: 10.
External routines: Cython1, h5py2, matplotlib3, NumPy4, mpi4py5
Nature of problem: Classical electrodynamics
Solution method: Finite-Difference Time-Domain (FDTD)
Running time: Problem dependent
References:1Cython, http://www.cython.org2h5py, http://www.h5py.org3matplotlib, http://www.matplotlib.org4NumPy, http://www.numpy.org5mpi4py, http://mpi4py.scipy.org
Drawing on social exchange theory and the service-dominant logic framework this paper explores the association between value co-creation and the willingness to engage in customer citizenship behavior ...in the hospitality and tourism context. Tourism and hospitality firms are increasingly offering opportunities for co-production and value-in-use not only to increase revisit and repurchase intentions but also to benefit from manifestations of customer citizenship behavior such as customer feedback, advocacy, customer-to-customer assistance and tolerance in less satisfactory future services. The paper offers a building block for future work to investigate the causal relationship between the dimensions of value co-creation (co-production and value-in-use) and customer citizenship behavior.
•Value co-creation is correlated with willingness to engage in customer citizenship behavior.•Value co-creation is correlated with guest satisfaction.•Guest satisfaction is correlated with willingness to engage in customer citizenship behavior.•Social exchange theory can explain the relationship between these variables.
A three-dimensional (3-D) finite-difference time-domain (FDTD) algorithm is used in order to simulate ground penetrating radar (GPR) for landmine detection. Two bowtie GPR transducers are chosen for ...the simulations and two widely employed antipersonnel (AP) landmines, namely PMA-1 and PMN are used. The validity of the modeled antennas and landmines is tested through a comparison between numerical and laboratory measurements. The modeled AP landmines are buried in a realistically simulated soil. The geometrical characteristics of soil's inhomogeneity are modeled using fractal correlated noise, which gives rise to Gaussian semivariograms often encountered in the field. Fractals are also employed in order to simulate the roughness of the soil's surface. A frequency-dependent complex electrical permittivity model is used for the dielectric properties of the soil, which relates both the velocity and the attenuation of the electromagnetic waves with the soil's bulk density, sand particles density, clay fraction, sand fraction, and volumetric water fraction. Debye functions are employed to simulate this complex electrical permittivity. Background features like vegetation and water puddles are also included in the models and it is shown that they can affect the performance of GPR at frequencies used for landmine detection (0.5-3 GHz). It is envisaged that this modeling framework would be useful as a testbed for developing novel GPR signal processing and interpretations procedures and some preliminary results from using it in such a way are presented.
Purpose
Drawing on the service-dominant logic and the institutional theory, this paper aims to explore the value-creating mechanisms of branding in the destination context and the brand co-creation ...process at and between different levels of a service ecosystem.
Design/methodology/approach
An exploratory research design was used to generate qualitative data from 18 in-depth interviews with important stakeholders and investigate how and why brand co-creation is fostered in the service ecosystem.
Findings
The study proposes a stepwise process of strategic imperatives for brand co-creation in the destination context. It presents the multi-directional flows of the brand meaning across levels of the tourism ecosystem and thereby interprets stakeholders’ efforts to co-create sustainable brands that gain prominence in the global tourism arena.
Research limitations/implications
Future research might validate the framework in a quantitative research setting. The extended analysis of the value-creating ecosystem could investigate the role of institutions and brand value propositions across levels.
Practical implications
Acknowledging their limited control over the brand co-creation process, tourism practitioners are offered step-by-step guidance to help shape a destination brand that may retain relevance in the tourists’ minds. Critical insights are provided into resource sharing between actors and subsequent responsibilities for a sustainable destination branding strategy.
Originality/value
The paper considers the significance of the various levels in the ecosystem and the underlying mechanisms of brand co-creation in a somewhat neglected branding domain.
Estimating the permittivity of heterogeneous mixtures based on the permittivity of their components is of high importance with many applications in ground penetrating radar (GPR) and in ...electrodynamics-based sensing in general. Complex Refractive Index Model (CRIM) is the most mainstream approach for estimating the bulk permittivity of heterogeneous materials and has been widely applied for GPR applications. The popularity of CRIM is primarily based on its simplicity while its accuracy has never been rigorously tested. In the current study, an optimised shape factor is derived that is fine-tuned for modelling the dielectric properties of concrete. The bulk permittivity of concrete is expressed with respect to its components i.e., aggregate particles, cement particles, air-voids and volumetric water fraction. Different combinations of the above materials are accurately modelled using the Finite-Difference Time-Domain (FDTD) method. The numerically estimated bulk permittivity is then used to fine-tune the shape factor of the CRIM model. Then, using laboratory measurements it is shown that the revised CRIM model over-performs the default shape factor and provides with more accurate estimations of the bulk permittivity of concrete.
A new simple formulation for incorporating a higher-order perfectly matched layer (PML) stretching function within a convolution PML (CPML) implementation in finite-difference time-domain (FDTD) ...electromagnetic modeling codes is developed. Obtaining in closed form the corresponding time domain impulse response of the inverse of a number of higher-order PML stretching functions enables the efficient and simple implementation of such higher-order PMLs using recursive convolution, in the same way as it was introduced initially for the complex frequency shifted (CFS) PML. This new higher-order CPML exhibits excellent performance that is comparable to the performance shown by other higher-order PML formulations whilst it retains the advantage of a relatively simpler implementation.
The way in which electromagnetic fields are transmitted and received by ground penetrating radar (GPR) antennas is crucial to the performance of GPR systems. Simple antennas have been characterized ...by analyzing their radiation patterns and directivity. However, there have been limited studies that combine real GPR antennas with realistic environments, which is essential to capture the complex interactions between the antenna and surroundings. We have investigated the radiation characteristics and sensitivity of a GPR antenna in a range of lossy dielectric environments using both physical measurements and a three-dimensional (3-D) finite-difference time-domain (FDTD) model. Experimental data were from measured responses of a target positioned at intervals on the circumference of a circle surrounding the H-plane of the antenna. A series of oil-in-water emulsions as well as tap water were used to simulate homogeneous materials with different permittivities and with complex conductivities. Numerical radiation patterns were created utilizing a detailed 3-D FDTD model of the antenna. Good correlation was shown between the experimental results and modeled data with respect to the strength of the main lobe within the critical angle window. However, there are discrepancies in the strength of main lobe at shallow angles. In all the dielectrics, the main lobes are generally broad due to the near-field observation distance but, as expected, become narrower with increasing permittivity. These results provide confidence for further use of the FDTD antenna model to investigate scenarios such as larger observation distances and heterogeneous environments that are difficult to study experimentally.
Sarcopenic obesity (SO) constitutes the coexistence of skeletal muscle mass loss (sarcopenia) and excess adiposity (obesity). It is mainly considered as a condition in the elderly with ...health-threatening impacts ranging from frailty to mortality. Mitochondrial dysfunction consists one of the basic pathophysiological mechanisms leading to the development of SO and its consequences. Indirect indicators of mitochondrial function, such as VO2max and exercise capacity, have been demonstrated to be negatively affected in individuals with SO, while the positive effect of exercise on mitochondrial function has been widely proved; thus, in this review, we aimed at investigating the effects of endurance, resistance, and concurrent exercise training on indexes of mitochondrial dysfunction in SO patients. The results of the clinical trials evaluated reveal positive effects of chronic exercise on VO2max and physical capacity, as well as mitochondrial biogenesis and activity. It has been concluded that utilizing a systematic exercise training program that includes both aerobic and strength exercises can be an effective strategy for managing SO and promoting overall health in these patients.
Two particle image velocimetry (PIV) softwares applied to turbulent flows are compared. One is based on a standard cross-correlation (CC) algorithm and the other is based on an iterative ...multi-pyramid optical flow (OF) algorithm. First, still particle images are used to evaluate the cut-off frequency induced by each method. Then a step response analysis highlights the capabilities of each method to minimise the effect of unresolved velocity gradients. Two different benchmarks with various turbulent length-scales, down to the Taylor microscale, are then used to analyse the velocity spectra and the turbulent kinetic energy dissipation estimation. First, a synthetic PIV dataset of homogeneous isotropic turbulence is processed and compared with direct numerical simulation (DNS) results. Then a grid turbulence wind tunnel experimental dataset is used to calculate velocity spectra and second-order structure functions, which are compared to laser Doppler velocimetry spectra. All these results point to the fact that, although OF is more diffusive and up to 5% less accurate than cross-correlation, the numerical diffusion improves the calculation of sub-window unresolved gradients and allows for direct and more robust measurement of the onset of the viscous subrange in experimental turbulent flows.
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